Lining for installations for the degasification of metals



June 20, 1967 s. KIENOW 3,326,543

LINING FOR INSTALLATIONS FOR THE DEC'ASIFICATION OF METALS Filed Oct. 2,1964 Sigismund Kienow IN VENTOR.

ATTORNEYS United States Patent 3,326,543 LINING FOR INSTALLATIONS FORTHE DEGASIFICATION 0F METALS Sigismund Kienow, Wiesbaden, Germany,assignor to Didier-Werke A.G., Wiesbaden, Germany Filed Oct. 2, 1964,Ser. No. 401,136 7 1 Claim. (Cl. 266-35) This application is acontinuation-in-part of my application Ser. No. 111,149 filed May 19,1961, entitled Lining for Installations for the Degasification ofMetals, now abandoned.

The present invention relates to a lining particularly designed for thevacuum or degasification chamber in installations for the degasificationof metals, particularly steel.

It is an object of the invention to provide a lining capable ofwithstanding a considerably increased number of charges, particularly inperiodically operated installations.

The revolving degasification process which is used lately for the vacuumsteel degasific-ation consists in that an evacuated degasificationvessel with two tubes which extend substantially vertically towards thebottom is immersed from the top into the fluid melt which is to bedegasified and the melt is brought into circulation by means of aconveying gas.

This process has proved to be advantageous for larger quantities ofmelting masses for charges of 40 tons and above. The degasificationprocess requires a relatively minor time of duration of about tominutes. The quality and the gas content of the melt are considerablyimproved. For the degasification the melt is cut off into a castingladle, whereby the temperature is chosen a little bit higher than thepouring. This surplus temperature has to be sufficient in order toaccomplish the vacuum treatment according to the revolving process. Itis therefore easier to treat larger charges with a higher heat contentthan smaller charges with a correspondingly lower heat content. Forthese smaller charges the temperature has to be chosen accordingly highenough, which is not of advantage for all kinds of steel.

These disadvantages are avoided in a simple way in that for thecontainer for the melt a melting furnace is used which is heated in theknown way, but which is not provided with a jacket sealing the sametowards the atmosphere.

As a container for the melt any desired heated ladle of a meltingfurnace can be used. For the heating, a simple heating by means of a gasburner is used, for instance, but preferably an induction furnace ladle.This kind of heating has the special advantage that it promotes theagitating effect and the intermixing of the degasific'ation process.

Vacuum vessels in installations of the above type for the degasificationof metals, especially for steel, for instance such as are described inLuxembourg Patent 34,978, in German Design Patent 1,820,854 and inGerman patent application DAS 1,098,971 consist, as shown in theattached drawing, of the steel jacket 1 and the steel cover 2 which isbolted onto the jacket 1 by the flanges 4. The abutment ring 3 is madeof steel. The fireproof insulating masonry is shown at 6 and themagnesite masonry 7 consists of magnesite bricks of low iron content.Between the insulating masonry 6 or the abutment ring 3 and the cover 2or jacket 1 is a cavity 5.

A connecting member 8 is attached to the bottom of the vessel whichconsists of the steel tube 12 having holding pins 11. The inside of thesteel tube is either fully or partially lined with corundum bricks 9which are produced by fusing corundum with aluminum oxyhyice droxide asa binding agent. There is also the possibility of lining the upperportion of the tube 12 with magnesite bricks of low iron content. Theouter lining of the steel tube 12 consists of a high aluminiferousramming mass 10 which is retained by the holding pins 11.

The connecting member is mounted upon the steel jacket 1 by the flange13. A closable opening 14 is provided in the side masonry 6 throughwhich a graphite bar (not illustrated) may be introduced into theVessel. In the masonry ceiling 7 and in cover 2 an opening 15 isprovided at which the vacuum duct (not illustrated) of the vacuum unit(also not illustrated) is connected. This vacuum duct is mounted uponcover 2 in a manner which is also not illustrated.

If such periodically operating vacuum vessels, as is customary inEurope, are supplied with iron oxide-rich magnesite bricks of thefollowing composition:

they would not withstand more than 50 to 70 charges. Periodicallyoperated installations are for instance such, as are described in theabove Luxembourg Patent 34,978. The reason for the premature failure isthat the Fe O contained in the brick is during degasification reduced toFe(), and finally to metallic Fe. In reverse order, Fe is oxidized up toFe O when air is present in the degasifica tion vessel. The changesoccurring in volume cause grinding of the bricks, and exfoliation.

It has been found that the durability of the lining can be considerablyincreased, when instead of magnesite bricks which are nowadayscommercially sold, use is made of those which have a Fe 0 content of notabove 2 percent and preferably those practically free from iron oxide.

A vacuum vessel which was lined with magnesite bricks having a Fe Ocontent of below 2% did not show any corrosion after 192 charges on theside walls. The bottoms were only slightly corroded. The device couldhave continued operation without any repairs for a considerable numberof further charges.

The other ingredients of the magnesite CaO, A1 0 and Si0 influence thedurability only to a minor extent. But, by diminishing theseconstituents a considerable improvement of the durability can beobtained. A lining from magnesite bricks with constituents of Fe O below2 percent, SiO below 2 percent, A1 0 below 2 percent, CaO below 1percent and MgO of percent resisted, for instance, 351 charges. At suchtime, a complete renewal of the bottom was necessary. The other parts ofthe lining could have been further used, but, they were also replaced.

Chemically bound magnesite bricks, also such as those with theconstituents of foreign oxides which were below the above mentionedvalues, did not prove suitable for the lining of vacuum vessels ininstallations for the degasification of metals, especially steel. Thebricks, generally, have to be sintered advantageously at temperatures of1600 C. and higher. With bricks which were sintered at 1650 C. and whichhad the composition of 95% MgO, 0.5 Fe O 2% SiO 2% A1 0 0.5% CaO 321charges could be accomplished.

The porosity of the bricks shall advantageously be at most 20% byvolume. Bricks which were sintered at 1650 C. and having saidcomposition and a porosity of 18% by volume resulted in 356 charges,bricks with the same composition, but with a porosity of 22% by volumeresulted in only 323 charges.

3 The described bricks are especially advantageous for the'lining of thebottom and the side walls of degasification chambers. Said bricks aremanufactured, for example, as follows:

Sinter calcined ata temperature of 1800 consisting of sea-water magnesiaor impervious natural magnesite or fusion magnesia is crushed and sievedso that a fraction of -4 mm. and fine flour of 0-05 mm. result. Thefractions are mixed in a pan grinder in such ratio that the mass afterthe grinding contains 28 to 30% of flour below 0.09 mm. As binding agentthere are added 2% of sulphite solution. It is important that no otherbinding agent such as silicate, alumina, etc., are added which wouldreduce the chemical purity and thus result in an increased attack by theusually alkali-richslag, and further in a decrease of the volumeconsistency of the bricks during operation.

The mass is pressed under a pressure of 1000 kg/cm.

in a hydraulic press to shaped bricks, or rammed with the compressed-airgun and is subsequently calcined in the tunnel kiln at a temperature of1620 C.

The ceiling or arched roof of the. vessel should be advantageously linedwith magnesite bricks which have a high resistance towards temperaturechanges, for instance such as those consisting of coarse magnesitegranules and fine magnesite granules, lacking medium granules, as forinstance those consisting of above 70% magnesite sinter having a granulesize of '1 to 4 mm. and 30% magnesite sinter having a granule size below0.2 mm. It is not necessary, thereby, that these bricks are alsoprovided with a minor portion of foreign oxides, especially Fe O andCaO, such as the ones which are used for the bottom and the side walls.Also, the porosity can be higher and the sintering temperature can belower. Chemically bound bricks are not suitable for the ceiling e.g.arched roof. But, advantageously, the bricks for the ceiling or archedroof shall have the same chemical composition and same low porosity asthe bricks for the bottom and the side walls and shall be sinteredequally high.

The ports or sockets which are arranged below the vacuum vessel, mayalso be lined with magnesite bricks as suggested according to thepresent invention for the bottom and the side walls. In this portion ofthe vessel there is a strong change in temperature and further anintensive attack by the passing steel flow and slag. A magnesite brickdoes not withstand such attacks. Of special advantage for the lining ofthe ports are corundum bricks with as minor a constituent of foreignoxides a possible, such bricks are, for instance, manufactured as beunderstood from the foregoing description and it is apparent thatvarious. changes maybe made in the construction and arrangement of theparts without departing from the spirit and scope of the invention orsacrificing its material advantages, the form and the articlehereinbefore described being merely a preferred embodiment of" theinvention.

I claim:

A vacuum receptacle for installations for the degassing of metals,especially iron, comprising a kettle and a connecting piece, said kettlebeing lined withbaked magnesite bricks which contain at least MgO andnot more than 2% Fe O 2% SiO 2% A1 0 and 1% CaO, and

said connecting piece being lined with corundum bricks consisting onlyof corundum.

References Cited UNITED STATES PATENTS 2,043,029 6/ 1936 Blau et a1.10665 X 2,572,688 11/1951 Austin 106-58 2,579,781 12/1951 Austin et al10658 2,733,913 2/1956 Mercer 26643 2,823,134 2/1958 Atlas 106-583,030,228 4/1962 Hernandez et a1. l06-58 X 3,067,050 12/1962 Miller106-65 3,153,110 10/1964 Sherburn et al. 26635 X CHARLIE T. MOON,Primary Examiner.

TOBIAS E. LEVOW, Examiner.

I. E. POER, Assistant Examiner.

